Multi-Layer Encapsulated Structures

ABSTRACT

An electroplating method that includes: a) contacting a first substrate with a first article, which includes a substrate and a conformable mask disposed in a pattern on the substrate; b) electroplating a first metal from a source of metal ions onto the first substrate in a first pattern, the first pattern corresponding to the complement of the conformable mask pattern; and c) removing the first article from the first substrate, is disclosed. Electroplating articles and electroplating apparatus are also disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/441,573 (Microfabrica Docket No. P-US002-U-SC), filed Apr. 6, 2012.The '573 application is a continuation of U.S. patent application Ser.No. 13/167,451 (Microfabrica Docket No. P-US002-S—SC), filed Jun. 23,2011. The '451 application is a continuation of U.S. patent applicationSer. No. 11/927,369 (P-US002-P-SC), filed Oct. 29, 2007, now U.S. Pat.No. 7,981,269, issued on Jul. 19, 2011. The '369 application is acontinuation of U.S. patent application Ser. No. 11/622,279(P-US002-J-SC), filed Jan. 11, 2007, now abandoned. The '279 applicationis a continuation of U.S. patent application Ser. No. 10/677,409(P-US002-1-SC), filed Oct. 1, 2003, now abandoned. The '409 applicationis a continuation of U.S. patent application Ser. No. 09/493,496(P-US002-E-SC), filed Jan. 28, 2000, now U.S. Pat. No. 6,790,377, issuedon Sep. 14, 2004. The '496 application is a divisional of U.S. patentapplication Ser. No. 09/055,183 (P-US002-A-SC), filed Apr. 3, 1998, nowU.S. Pat. No. 6,027,630. The '183 application claims priority to U.S.Provisional Patent Application No. 60/043,742, filed on Apr. 4, 1997.Each of these prior applications is incorporated herein by reference asif set forth in full.

BACKGROUND OF THE INVENTION

The invention relates to forming structures by electrochemicaldeposition.

Microfabrication processes (also referred to as micromachining) arebeing developed and refined for eventual application to the manufactureof complex devices including machines and instrumentation. Theseprocesses are being directed to the production of machines ofminiaturized devices having features in the range of a few microns andin some cases features in the submicron range, some of which currentlyexist on a macroscopic scale.

Microfabrication processes include: bulk micromachining, in whichmaterial is removed from regions of a substrate; surface micromachining,in which a thin conformal structural layer and one or more sacrificiallayers are deposited onto a substrate; and LIGA, which generates 2.5-Dextruded shapes by molding materials around metals molds which wereformed by the metals being electrodeposited within openings in thicksynchrotron-processed photoresists. These processes are used to producestructures of simple geometries (e.g., they can be defined by 1-4different cross sections), and are usually customized for eachapplication.

Solid freeform fabrication, which is also referred to as rapidprototyping, is used to manufacture macroscopic parts from hundreds oflayers by generating one layer at a time. These processes producefeatures typically greater than 50-100 um in width using layerstypically greater than 50-150 um thick. These processes typicallygenerate a layer serially. These processes employ structures forsupporting the part being manufactured. The support structures are oftencustomized to the part.

SUMMARY OF THE INVENTION

In one aspect, the invention features an electroplating method thatincludes: a) contacting a first substrate with a first article, whichincludes a substrate and a conformable mask disposed in a pattern on thesubstrate; b) electroplating a first metal from a source of metal ionsonto the first substrate in a first pattern, the first patterncorresponding to the complement of the conformable mask pattern; and c)removing the first article from the first substrate.

In preferred embodiments, the method further includes electroplating asecond metal from a second metal ion source onto the first substrate. Inone embodiment, the step of electroplating the second metal includes: a)contacting the first substrate with a second article including asubstrate and a conformable mask disposed in a pattern on the substrate;b) electroplating a second metal onto the first substrate in a secondpattern, the second pattern corresponding to the complement of theconformable mask pattern of the second article; and c) removing thesecond article from the first substrate. The method can further includebuilding additional layers.

In one embodiment, the invention features an electroplating method thatincludes repeatedly contacting a substrate with a patterned conformablemask; electroplating a first metal form a source of ions onto thesubstrate in a pattern, the pattern corresponding to the complement ofthe conformable mask pattern; and removing the mask from the substrate.

In another embodiment, the invention features a method for manufacturingan element that includes forming a multi-layer structure by repeatedlyforming layers according to the above-described electroplating methods.

In another aspect, the invention features an electroplating article thatincludes a substrate having a first major surface and a conformable maskdisposed in a pattern on the first major surface of the substrate. Thearticle is capable of electroplating a pattern of metal complementary tothe pattern of the conformable mask onto an electrode when the articleis placed in contact with the electrode in the presence of a metal ionsource and subjected to an electric field.

In other aspects, the invention features an electroplating apparatusthat includes an electrolyte, which includes ions of a first metal andions of a second metal, an anode in contact with the electrolyte, acathode in contact with the electrolyte, and a first article (e.g., theabove described electroplating article) in contact with the electrolyte.

In one embodiment, the electroplating apparatus includes a firstelectroplating reservoir that includes an electrolyte, which includes afirst metal ion, disposed within the first reservoir, an anode incontact with the electrolyte, a cathode in contact with the electrolyte,and an article (e.g., an article described above) in contact with theelectrolyte; a second electroplating reservoir that includes anelectrolyte, which includes ions of a second metal, disposed within thesecond reservoir, and an anode in contact with the electrolyte.

In another aspect, the invention features a method for manufacturing anelectroplating article. The method includes: a) applying a conformablemask to an article comprising a first substrate and a patterned resistdisposed on the first substrate; b) contacting a second substrate tosaid conformable mask such that the conformable mask obtains a patterncomplementary to the resist pattern; c) separating the first substratefrom the conformable mask (the conformable mask remaining adhered to thearticle); and d) removing the resist.

In one embodiment, the method for manufacturing an electroplatingarticle includes providing a porous medium having a first surface; b)treating said porous medium to create one or more nonporous regions; c)applying a film to said first surface of said porous medium; d)patterning the film to create a patterned mask; and e) removing at leasta portion of the one or more nonporous regions.

In other aspects, the present invention is directed to the calculation,storage and retrieval of cross section geometry of a three dimensionalobject for generation of patterned masks reflecting that geometry andfor use in an electroplating method. The data and control processes ofvarious embodiments of the invention can be implemented by a softwareapplication program executed in a general purpose computing system.

The data and control processes of various embodiments of the inventioncan be embodied in an electroplating method implemented via theapplication program and also in an article of manufacture, in the formof a data storage medium that stores application program code arrangedto carry out that method upon execution by a processor.

The electroplating methods and articles allow fabrication of devicesfrom thin layers of materials such as, e.g., metals, polymers, ceramics,and semiconductor materials. The electroplating methods producerelatively homogeneous, isotropic elements (e.g., devices) withoutinterlayer junctions. The electroplating methods can be performed at lowtemperatures, thus allowing substrates such as integrated circuits andsilicon wafers to be used as plating substrates.

The electroplating methods of various embodiments of the invention canbe used to fabricate devices of freeform geometry including high aspectratio devices, hollow devices with internal features, devices withcantilevered and “chandelier” geometries, and functional assemblies ofinterconnected, stationary or moving parts (i.e., devices fabricated inan assembled state). The electroplating articles, apparatus, and methodsalso are particularly useful in mass production of devices.

Other features and advantages of various aspects of the invention willbe apparent from the following description of the preferred embodimentsthereof, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is view taken in cross section of an electroplating articleaccording to one embodiment of the invention;

FIG. 2 is a view taken in cross section of an electroplating articleaccording to a second embodiment of the invention;

FIGS. 3 a-3 d are diagrams of a first embodiment of a method for formingan electroplating article;

FIGS. 4 a-4-e are diagrams of a second embodiment of a method forforming an electroplating article;

FIGS. 5 a-5 e are diagrams of a third embodiment of a method for formingan electroplating article;

FIGS. 6 a-6 d are diagrams of a fourth embodiment of a method forforming an electroplating article;

FIGS. 7 a-7 f are diagrams of a fifth embodiment of a method for formingan electroplating article;

FIGS. 8 a-8 e are diagrams of a sixth embodiment of a method for formingan electroplating article;

FIGS. 9 a-9 c are diagrams of a seventh embodiment of a method forforming an electroplating article;

FIGS. 10 a-10 c are diagrams of a method for forming a deposit accordingto an electroplating method of an embodiment of the invention;

FIGS. 11 a-11 m are diagrams of a method according to the electroplatingmethod of an embodiment of the invention;

FIGS. 12 a-12 c are diagrams of a method according to the electroplatingmethod of an embodiment of the invention;

FIGS. 13 a-13 i are diagrams of a method for fabricating an element onan integrated circuit;

FIGS. 14 a-14 e are diagrams of a method for assembling elementsfabricated together;

FIGS. 15 a-15 b are diagrams of an element manufactured according to theelectroplating method of an embodiment of the invention;

FIGS. 16 a-16 d are views taken in cross section of elementsmanufactured according to one embodiment of the invention;

FIG. 17 is an electroplating apparatus according to one embodiment ofthe present invention;

FIG. 18 is a view taken in cross section of a substrate in contact withan electroplating article;

FIG. 19 is a top view of a portion of an electroplating apparatus of anembodiment of the invention;

FIG. 20 is a top view of a portion of an electroplating apparatusaccording to an embodiment of the present invention;

FIG. 21 is a top view of a portion of an electroplating apparatusaccording to an embodiment of the present invention;

FIG. 22 is a view taken in cross section of an electroplating articleholder of an embodiment of the present invention;

FIG. 23 is a view taken in cross section of an electroplating apparatusof an embodiment of the present invention;

FIG. 24 is a highly enlarged view taken in cross section of a substratein position in the electroplating apparatus of FIG. 23;

FIG. 25 is a view taken in cross section of a portion of anelectroplating apparatus of an embodiment of the invention;

FIG. 26 is a view taken in cross section of another portion of theelectroplating apparatus of FIG. 25;

FIG. 27 is a diagram of a three dimensional object (shown in twodimensions) with cross section lines indicated;

FIG. 28 is a functional block diagram of a computing system configuredfor calculation of cross sections of a three dimensional structure andfor driving an electroplating apparatus of an embodiment of the presentinvention;

FIG. 29 is a flow diagram illustrating a method for generating maskpattern files and apparatus control files;

FIG. 30 is a flow diagram illustrating a method for manufacturing athree dimensional object;

FIG. 31 is a view taken in cross section of an electromagnetic motor;

FIGS. 32 a-32 d are diagrams of an electroplating method employing morethan one article according to a third embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The embodiments feature electroplating methods, apparatus and articlesthat enable the manufacture of elements having complex structures. Theelectroplating methods include selective electroplating of layers thatmay include both structural materials (e.g., metals) and support (i.e.,sacrificial) materials; and subsequent removal (e.g., by etching,melting, or electrolytically dissolving) of the support materials. Thestructural material remaining after removal of the support materialdefines an element such as a microscopic or mesoscopic device. Theelectroplating methods employ electroplating articles that include apatterned conformable mask, optionally adhered to a support such as anelectrode or a porous medium.

In general, various embodiments of the invention feature electroplatingarticles for use in electroplating methods. The electroplating methodoccurs in an electroplating apparatus that includes an electroplatingbath filled with electrolyte, an anode, and a cathode. The electrolytecontains metal ions and, optionally, other additives. The anode can bepart of the electroplating article, as described below, or can belocated at a distance from the article. Throughout this application, thesubstrate to be plated functions as the cathode unless otherwisespecified. To simplify the description, the materials are referred to asmetals and similar features are indicated with the same referencenumerals.

Electroplating Article

Referring to FIG. 1, electroplating article 4, of a preferred embodimentof the invention includes a patterned conformable mask 6 adhered to asupport 8. The electroplating article can also be only a patternedconformable mask (i.e. without a support). The support can be a porousmedium (e.g., a filter), an anode, and combinations thereof. The articlecan include a plurality of different mask patterns on a single support.The different mask patterns can be contacted by a substrate in apredetermined sequence to sequentially plate a plurality of metal layerswhere each metal layer has a pattern corresponding to the complement ofthe mask pattern contacted, to form a multi-layered element. Referringto FIG. 2, electroplating article 4 can include one or more edge masks13 on the outer surface of the article, for confining the metal beingplated.

Contact between the electroplating article and the substrate to beplated is made by pressing the patterned mask against the substrateusing a well-controlled, uniform pressure. The appropriate maskingpressure will prevent flash (i.e., the deposition of metal in the areacovered by the mask), and will prevent distortion of the featuresdefined by the mask. When the electroplating article is removed fromcontact with the substrate, the mask remains adhered to the support andthus remains part of the electroplating article.

A variety of methods can be used to improve release of the mask from thesubstrate to be plated so as to prevent delamination of the mask fromthe support: for example, gradually peeling the electroplating article(if flexible) off of the substrate optionally with the aid of a dullblade; adding a non-stick/lubricating compound to the electrolyte;coating the mask surface with a non-stick composition (e.g., sputteredpolytetrafluoroethylene); and vibration (e.g., ultrasound).

Patterned Conformable Mask

The patterned conformable mask is sufficiently deformable (e.g.,elastically deformable) to permit conformance of the mask to the surfaceof a substrate to be plated to maximize contact between the mask and thesubstrate, and to minimize (preferably eliminate) the presence of gapsbetween the mask and the substrate. Maximizing contact between the maskand the substrate minimizes the potential for flash formation. The maskis also sufficiently durable to enable repeated use (i.e., contactingwith and removing from a substrate). The mask is sufficiently rigid andthin to prevent distortion of the mask features (i.e., the positive andnegative features constituting the closed and open features of the maskpattern respectively) by the masking pressure. The mask preferably isrelatively thick compared to its peak and valley roughness and thecurvature of the substrate to be plated.

The mask preferably exhibits very high volume electrical resistivity(e.g., 1014 Ohm-cm), has a very low permeability to ions in theelectrolyte solution, and is chemically non-reactive with the platingelectrolytes at the temperatures at which the plating operation isconducted. The mask can be hydrophilic or hydrophobic, with hydrophilicbeing preferred. In the case of hydrophobic materials, relatively higheramounts of wetting agents can be included in the electrolyte to ensurewetting of the mask material.

The mask preferably is capable of forming a strong bond (e.g., achemical or mechanical bond) to the support, such that small (e.g.,15×15 μm) isolated positive features are not delaminated by the maskfabrication process, normal handling of the mask or by removal of themask material from the substrate to be plated.

The patterned mask is preferably substantially planar and smooth toenable conformance to the substrate to be plated. The mask is capable ofbeing patterned with negative and positive features of varyingdimensions (e.g., 10-25 um or smaller, such as submicron), preferablywith no mask residue blocking the negative features of the mask pattern.The pattern of the mask includes apertures (i.e., negative features)extending through the mask thickness and defined by one or moresidewalls of the mask. The mask features preferably have a substantiallyplanar wall profile and may have a slight wall angle. The wall angle maybe slightly divergent toward the substrate to be plated, i.e. thenegative features are slightly larger at the substrate than at thesupport. Such wall angles may aid in separating the mask from thesubstrate and may aid in facilitating re-contacting the mask to thesubstrate in the presence of an existing deposit.

The mask can be compound so as to include more than one layer ofmaterial, e.g., a relatively rigid layer (e.g., a high aspect ratiophotoresist, e.g., SU-8 commercially available from MicroChemCorporation or synchrotron-processed polymethylmethacrylate), and aconformable layer. Another example of a useful rigid layer is a positivephotoresist such as Clariant AZ4620, which can be patterned by exposingit to ultraviolet light through the patterned conformable layer.

Examples of useful masking compositions for conformable portions of themask include elastomers such as, e.g., polydimethylsiloxane (i.e.,silicone rubber) commercially available, e.g., under the tradedesignation Sylgard from Dow-Corning (e.g., Sylgard 182 and 184), andunder the trade designation RMS-033 from Gelest. The maskingcompositions can include other additives, e.g., photoinitiators,fillers, and hydrogen getters.

Porous Medium

The porous medium has interconnected pores and is permeable to ions andadditives present in electrolyte compositions. The porous medium canhave one or more layers of varying porosity. The porous mediumpreferably has a pore size considerably finer than the minimum negativefeature of the mask. The pores are preferably uniform in open area,e.g., the open area of any 20 μm square of the medium is consistent to1%. Particularly useful porous mediums may be porous mediums that areuseful as filters, and particularly those that have a particle retentionrating in the range of 0.3-3 μm. For those porous mediums that includemultiple porous layers, each porous layer can vary in porosity and poresize, with the porous medium in closest proximity to the substrate to beplated exhibiting the above characteristics. The surfaces of the porousmedium that contact the mask should be sufficiently flat and smooth toensure that the surface of the adhered mask that contacts the substrateto be plated is also flat and smooth.

The porous medium is chemically non-reactive with the electrolytesolution at the operating temperature of the electrolyte bath. Preferredporous mediums are hydrophilic. The porous medium preferably ispermeable to gas to allow venting of gas bubbles generated during theelectroplating method.

Preferably the porous medium is free from shedding (i.e., does notrelease portions of itself into surrounding fluid), and is sufficientlydurable so as to withstand multiple electroplating operations. Examplesof suitable porous medium materials include rigid, hydrophilic, slipcast ceramic disk porous mediums (commercially available from CoorsCeramics) and hydrophilized membrane porous mediums made from, e.g.,polypropylene (commercially available under the trade designation GHfrom Gelman), polyvinylidenefluoride (commercially available under thetrade designation Durapore from Millipore) and polytetrafluoroethylene(commercially available under the trade designation LCR from Millipore).Rigid porous mediums can provide masking pressure when supported bytheir edges alone.

Particularly useful highly permeable, porous mediums include relativelythin, flexible, porous membranes. Porous membranes can be combined witha more rigid porous medium, which serves as a backing to provide therequisite pressure for masking applications. The porous membrane can besandwiched between the more rigid porous medium and the mask and theporous medium can be used to supply the requisite masking pressure forthe plating operation. The more rigid porous medium can have arelatively more coarse (i.e., larger) porosity than that useful fordirect contact with the mask. Porous membranes can be integrated withthe mask composition (or transformed into a mask).

To assist handling, porous membranes can be installed in the drumheadfixture described below, or temporarily adhered to a rigid flatsubstrate (e.g., a silicone wafer, glass) with an adhesive composition(e.g., dry film photoresist). Porous membranes can be processed whileadhered to the substrate and, after processing, removed by dissolvingthe adhesive.

Masking pressure can be applied to the porous membrane by the momentumof a stream or jet of electrolyte impinging on the membrane from behind,optionally in combination with dense particles incorporated into theelectrolyte, and increasing the viscosity of the electrolyte, forexample, by the addition of a polymer. Masking pressure can also beapplied to the membrane by sealing the membrane against the walls of thetank of the electroplating system and then pressurizing the electrolyte,causing the membrane to be pushed against the substrate to be plated. Adummy substrate can be used when the substrate to be plated is smallerthan the porous medium to prevent the membrane from bulging.

One example of an electroplating method that employs a porous membraneincludes pressing a relatively more rigid porous medium against themembrane, applying current, depositing a metal for a period, removingthe current, withdrawing the rigid porous medium from contact with themembrane, slightly displacing the relatively more rigid porous medium inits own plane (e.g., in an orbital or linear fashion), and repeating thecycle. Displacing the relatively more rigid porous medium during eachcycle allows a different portion of the rigid porous medium to makecontact with the membrane. Preferably the mask/membrane separates fromthe substrate to be plated while the relatively more rigid porous mediumis separated from the membrane so as to allow exchange of fluids betweenthe microvolume and bulk electrolyte.

Another membrane plating method includes pressing a granular medium,tiny spheres, or rollers against the membrane using, e.g., a rigidscreen. The tiny spheres and rollers can be rotated in a pattern (e.g.,a linear pattern using linear movement or a circular pattern using anorbital movement) on the membrane continuously or intermittently so asto average the local non-uniformities in pore structure of therollers/spheres. Preferably the amplitude of movement is equal to (morepreferably several times greater than) the diameter of the sphere orcylinder. Preferably the spheres/cylinders are relatively small and themembrane is relatively thick. The spheres/cylinders can be made of themetal being plated.

Anode

The electroplating article can consist of a patterned mask on an anode.The anode can be soluble or insoluble, rigid or flexible, porous ornonporous, and can include an erodable layer (e.g., a metal layer)supported by a conductive material that does not erode (e.g., platinizedtitanium). The anode can be of any dimension including a thin flexiblesheet of metal.

A soluble anode will tend to erode during use. The anode can be“redressed” periodically by reversing the polarity of the anode andplating metal back onto the anode through the negative features of themask. The excess metal is supplied by the electrolyte in conjunctionwith another anode according to, e.g., through-mask plating processesused in electronics manufacturing. For a system in which the mask isphysically supported by and attached to a porous medium, and an anode islocated directly behind the membrane, moving the anode will preventlocalized erosion of the anode.

Forming Electroplating Articles

In general, methods for forming electroplating articles include applyinga solid mask or liquid masking composition to a support, i.e., an anode,a porous medium and combinations thereof. The solid mask can bepatterned prior or subsequent to attachment to the support. Liquidmasking compositions can be patterned on a non-porous substrate (e.g.,inert material, or a material that can be dissolved or melted (e.g.,substrates of plastic, lacquer, or low melting point alloy)), cured(e.g., crosslinked, polymerized, hardened, solidified, gelled, andcombinations thereof), and attached to a support or patterned andsolidified directly on the support.

Preparation of the Support

It is preferable to planarize the surface of the support that willreceive the mask, so as to provide a smooth flat surface for receivingthe mask. When applying the mask to an anode, it is preferable to firstprepare the anode surface so as to maximize adhesion to the mask.Examples of useful anode surface preparation methods include chemicalmicroetching, lapping, sandblasting, and sintering a thin layer ofpowder onto the surface. A chemical adhesion promoter (e.g., SylgardPrime Coat) can also be used.

A variety of methods can be used to maintain or improve adhesion of themask to a porous medium. These methods include melting the mask whilepressing it into the porous medium resulting in a mechanicalinterlocking of the mask with the porosity of the porous medium, andapplying an adhesive composition between the mask and the porous medium.Adhesion of the mask to the porous medium can also be enhanced byemploying an adhesive that is a meltable material (e.g., glass), whichcan be dry deposited (e.g., sputtered) onto the surface of the patternedmask. When using an adhesive composition, it is preferable to employmethods that confine the adhesive composition to the areas locatedbetween the mask and the support (e.g., preventing the adhesive frombridging a negative feature that is only a few microns wide).

Liquid masking compositions have a tendency to soak into (i.e.,uncontrollably absorb into) the pores of a porous medium. A variety ofmethods can be employed to reduce “soak in” in regions of the porousmedium that are to remain porous. Examples of suitable methods forpreventing soak in include: (1) supplying pressurized air to one side ofthe porous medium; (2) treating the porous medium with a temporaryfiller composition that soaks in and fills the pores and then solidifiesto form a barrier to penetration of the liquid masking composition; and(3) treating the porous medium with a temporary filler composition thatis immiscible with and denser than the liquid masking composition. Thesurface of the porous medium can be abraded after infiltrating the poreswith filler composition to expose uncoated and unfilled surfacesallowing direct adhesion of the mask to the support. The fillercomposition can be dissolved or otherwise removed from the porous mediumafter the liquid masking composition has been cured to a solid.

Examples of useful filler compositions include acetone-soluble waxes andlacquers, soluble waxes used for investment casting cores, water solublesalts, gels, Crystal Bond 509, soluble thermoplastics, and phase-changematerials (e.g., ice, electrorheological fluids).

Referring to FIGS. 3 a-3 d, one example of a method for rendering aporous medium temporarily nonporous using a filler composition includes:spinning a thin layer of a liquid filler composition 132 onto arelatively flat surface 131 (e.g., a silicon wafer) (preferably thethickness of the filler composition layer is adjusted so as to fill thepores of the porous medium to a predetermined height); contacting afirst surface 136 of porous medium 130 to the spun-on filler composition132 (FIG. 3 a); allowing filler composition 132 to seep into the poresof the porous medium to a predetermined height (FIG. 3 b); solidifyingthe filler composition 132; and applying (e.g., by spinning on) asufficient amount of liquid masking composition 134 to a second surface138 of the porous medium 130 opposite the first surface 136 throughwhich filler composition 132 entered the porous medium 130. Liquidmasking composition 134 is applied so as to produce a layer of maskingcomposition of desired thickness on the surface of the porous medium.The remainder of the liquid masking composition 134 can seep into theporous medium (for purposes of adhesion) only to the surface of thesolidified filler 132 (FIG. 3 c). The method further includes curing themasking composition 134; removing solidified filler 132; etching thenegative features of the mask through the layer of porous medium 130that is saturated with masking composition 134 to at least a depth atwhich the solidified filler 134 existed (FIG. 3 d).

Other methods for preventing or limiting soak in include restricting thevolume of liquid masking composition that is applied to the porousmedium to only a fraction of the pore volume in the porous mediumcausing the liquid to only partially fill the pores. One such methodincludes spraying a liquid masking composition onto the porous medium,while carefully controlling the flow rate and speed of the spraypattern. Another method involves spin coating the liquid maskingcomposition onto a non-absorbing sheet to obtain a uniform thin layer,and placing the porous medium in contact with the spun on liquid maskingcomposition. When the porous medium is peeled away from the sheet or thesheet is dissolved or melted, a thin coating of masking composition istransferred to the porous medium (i.e., the masking composition remainsadhered to the porous medium). The liquid masking composition can becured prior to or subsequent to removal of the sheet.

Another method for preventing soak in involves applying the liquidmasking composition to a porous medium while the porous medium isspinning at high speed; the centrifugal forces spread the maskingcomposition into a thin layer before it has had time to soak inexcessively.

Another approach to preventing soak in involves forming a barrier layerat or near the surface of the porous medium. After processing, thebarrier layer (and optionally, some of the porous medium) is removedfrom the negative features of the mask, so as to expose the porosity ofthe porous medium. Optionally, to improve adhesion of the mask to thesupport, the regions of the barrier layer that will correspond to thepositive features of the mask can be removed prior to application of themask. The barrier layer can be removed using various techniquesincluding, e.g., chemical etching, dry etching, ion milling, lasermachining, and melting (e.g., for thermoplastic based barriers). Thebarrier layer can also be formed by applying another material to thesurface of the porous substrate, e.g., (1) by laminating a film of asolid material, such as dry film photoresist onto the porous medium; (2)by applying a liquid barrier layer, preferably of high viscosity, usingone of the techniques discussed above that restrict soak-in volume; (3)by coating the porous medium with a thin layer of powder and melting thepowder layer so as to form a non-porous coating; (4) by depositing abarrier film by vacuum evaporation, sputtering, CVD, or other process;and (5) by using combinations thereof.

In the case of a porous anode, soak in can be prevented using a varietyof methods which include, for example, (1) applying a nonporous layer tothe surface of the porous anode and, after patterning the mask, removingthe nonporous layer in the negative areas of the mask to expose theanode; (2) sintering a partly-compacted powder of anode material in amold to create a sintered anode with an outer non-porous layer,patterning the mask from a masking material that is applied over thesintered material, and immersing the structure in an etchant thatattacks the metal of the anode, such that the outer non-porous layer ofsintered anode material is dissolved (in the unmasked regions); (3)melting the surface of the anode (e.g., by flame, or contact with a hotsurface), then patterning the mask and removing the melted surfacematerial to expose the porous anode material in unmasked regions; and(4) temporarily filling the surface pores with a material, e.g., metalelectrodeposited onto the porous surface, then patterning the mask andremoving the temporary filler material to expose the porous anodematerial in unmasked regions.

Patterning and Fabricating the Electroplating Article

A variety of methods can be used to pattern the electroplating article.Referring to FIGS. 4 a-4-e, an example of a method for forming anelectroplating article is shown. The method includes forming a micromold140 by coating (e.g., by spinning) a layer of resist 142 (e.g.,photoresist commercially available under the trade designation SU-8 5from MicroChem. Corp.) onto a substrate 144 (e.g., a silicon wafer)(FIG. 4 a). Preferably the layer of photoresist has a thickness a fewmicrons greater than that of the desired thickness of the final mask.The photoresist can be patterned using a photomask and a light source(e.g., a UV light source). A positive feature of the resist correspondsto a negative feature of the mask. Optionally, the micromold can be madefrom a non-stick material such as polytetrafluoroethylene orpolypropylene, and can include a pattern formed, e.g., by reactive ionetching or excimer ablation, or micromolded from a master mold accordingto processes similar to processes used in the fabrication of compactdisks.

The micromold surface including the photoresist and the substrate can bepassivated by allowing the micromold to be exposed to vapors of, e.g.,(tridecafluoro-1,1,2,2,-tetrahydrooctyl)-1-trichlorosilane (commerciallyavailable from United Chemical Technologies). A liquid maskingcomposition 146 is then poured over the raised pattern defined by thepatterned photoresist (FIG. 4 b). Support 148 is then pressed againstmicromold 140 (FIG. 4 c). Uniform pressure is applied such that liquidmasking composition 146 is forced out of the area 150 located betweenthe raised portions (i.e., positive features) of the resist pattern andthe surface of support 148. Preferably, liquid masking composition 146is completely squeezed out of the areas 150 corresponding to thepositive features of resist 142. The entire assembly 152 remains in thismating relationship until the liquid masking composition has cured. Fora heat-curable masking composition, the assembly can be transferred toan oven to cure.

In the case of a mask that has been cured in the oven, the assembly isquickly disassembled to minimize differential thermal contractionbetween support and the mold. The support and cured mask 156 is pulledaway from mold 140 such that cured mask 156 detaches from micromold 140,yet remains adhered to support 148 (FIG. 4 d). Mask 156 exhibits apattern inverse to that of micromold 140. Micromold 140 can be reused.After cure, before or after detachment of the mask and mold, excess maskmaterial 154 surrounding support 148 is removed as illustrated in FIG. 4e. If necessary, micromold 140 can be cleaned to remove mask residue.One example of a useful silicone cleaning composition is a siliconestripper, e.g., Amtex CCR (commercially available from Amtex ChemicalCorp.).

Any residual layer of masking composition remaining in negative features158 of mask 156 (FIG. 4 d) can be removed using dry etching (e.g., RIEwith a mixture of O2 and CF4 gas), which may also reduce the thicknessof the positive features of the mask. The result of such removal isdepicted in FIG. 4 e. Uniform etching extending to the edge of thesupport can be accomplished by surrounding the support with a “dummy”substrate preferably of similar composition, such that non-uniformitiesdue to edge effects are out of the area of interest.

When the mask is adhered to a porous medium, the etch may be continuedto remove any barrier layer present in the porous medium from thenegative features of the mask and may be continued until a porousportion of the porous substrate is removed. If pores in a porous mediumhave been filled or are non-existent, the pores are re-established orestablished, e.g., by reactive ion etching.

Another method for forming an electroplating article is shown in FIGS. 5a-5 e. The method includes patterning a photoresist 142 onto a support148 (i.e., the porous medium or the prepared anode) to the approximatethickness desired for the final mask (FIG. 5 a). The areas of support148 occupied by resist 142 correspond to negative features of the maskthrough which metal can be deposited. When patterning a porous mediumthat includes a barrier, the porous medium can be etched to remove thebarrier layer from those areas of the porous medium that are not coveredby resist. The method further includes applying a liquid maskingcomposition 146 to support 148 (FIG. 5 b), and optionally vacuumdegassing the masking composition. A flat, smooth, non-stick (e.g.,PTFE) sheet 160 is then pressed against resist 142, and liquid maskingcomposition 146 parallel to support 148 (FIG. 5 c), and pressure isapplied to squeeze the liquid masking composition 146 out from betweenresist 142 and sheet 160. Masking composition 146 is then cured, sheet160 is removed, and residual masking composition overlaying the resistis removed (FIG. 5 d), e.g., by etching (e.g., reactive ionizationetching using a mixture of O2 and CF4 gas). Resist 142 is then removedto expose areas of the support previously occupied by the resist (FIG. 5e). When patterning a porous medium, mask material that has seeped intothe negative features of the mask from neighboring positive features canbe removed by etching both mask and porous medium to the required depth.If pores of the porous medium have been filled or are non-existent, thepores can be established or re-established.

Referring to FIGS. 6 a-6 d, another method for forming an electroplatingarticle includes applying (e.g., by spinning on) a layer ofphotopatternable liquid masking composition 146, e.g., RMS-033(commercially available from Gelest) in combination with aphotoinitiator (e.g., 2,2-dimethoxy-2-phenyl acetophenone (commerciallyavailable from Polysciences, Inc.)), to support 148 (FIG. 6 a). Liquidmasking composition 146 can be covered with a thin, oxygen-impermeablefilm (e.g., Mylar) to protect the composition from contact with oxygen.Masking composition 146 is then exposed to patterned light (e.g., UVlight transmitted through a photomask 162) to selectively cure the maskcomposition (FIG. 6 b). The film is removed (FIG. 6 c) and thephotopatternable masking composition is developed (e.g., by dissolvingwith xylene) removing uncured masking composition 146 (FIG. 6 d). If anonporous barrier layer exists, it is removed (e.g., by dry etching)from the negative features of mask 156. Pores are established ifnecessary. For those photopatternable masking compositions that arenegative working the porous medium can be completely saturated withmasking composition until there is a surface layer of maskingcomposition having the desired thickness. After photopatterning, theunexposed masking composition material (including that in the pores) isdissolved in the developer.

When patterning a porous medium, the porous medium can be tinted a darkshade or coated with an antireflection composition to reduce the amountof light scattered from the textured surface.

Referring to FIGS. 7 a-7 f, another method for making an electroplatingarticle is shown. The method includes applying a liquid maskingcomposition 146 (or a solid mask material) to support 148 (FIG. 7 a);curing liquid masking composition to form an unpatterned solidified mask156; coating unpatterned mask 156 with either a thick resist 164 or athin resist disposed on a thin metal layer (not shown) (FIG. 7 b);patterning resist 164 and, in the case of a metal layer, using thepatterned resist to pattern the metal layer (e.g., by etching orlift-off) (FIGS. 7 c and 7 d); selectively removing (e.g. by wet etch,dry etch, or ion mill) portions of unpatterned mask 156 to form apatterned mask 156 using thick resist 164 (and metal layer if present)as a mask (FIG. 7 e); and in the case where the substrate is a porousmedium, preferably removing the top layer of the porous medium to openpores; and removing, e.g., by stripping, the remaining resist 16 a (andmetal layer if used) (FIG. 7 f).

Referring to FIGS. 8 a-8 c, a method for forming an electroplatingarticle is shown which includes: applying a liquid masking composition146 (or a solid mask material) to support 148 to the desired, thickness;curing (if liquid) the masking composition to form solidifiedunpatterned mask 156 (FIG. 8 a); applying a photomask 162 over the mask156 (FIG. 8 b) where the photomask has light apertures 166 and lightbarriers 168; exposing solid mask 156 to patterned ultraviolet lightthrough the photomask 162 (FIG. 8 c), the UV light having an intensityand wavelength suitable for ablating the mask and support material,e.g., a LTV excimer laser beam; ablating mask 156 until support 148 isexposed (FIG. 8 c); and, when patterning a porous medium, ablatingbarrier layer 170, if present (FIG. 8 d) and, if necessary, the toplayer of the porous medium to open pores; and removing the photomask toform the electroplating article 172 (FIG. 8 e).

Methods similar to methods used in relief printing can also be used tofabricate electroplating articles. One example of such a methodincludes: applying a liquid masking composition to a relief pattern,which might be produced by patterning a high aspect ratio photoresistsuch as AZ4620 or SU-8; pressing the relief pattern/masking compositionstructure against a support such that the masking composition adheres tothe support; and removing the relief pattern. The formed electroplatingarticle includes a support having a mask patterned with the inversepattern of the relief pattern.

Another example of such a method includes: creating a relief pattern onthe support by etching of the support, or by applying a durablephotoresist, e.g., SU-8 of desired configuration; coating a flat, smoothsheet with a thin, uniform layer of liquid masking composition; stampingthe support/resist against the coated sheet (e.g., like a stamp andinkpad) to quickly mate those portions of the liquid composition to thepositive features of the support/resist by unmating them from the smoothsheet (preferably the support and the sheet are kept parallel); andcuring the liquid masking composition.

Referring to FIGS. 9 a-9 c, a method for forming an electroplatingarticle is shown in which a surface layer of porous medium 148 issaturated with a liquid masking composition to the thickness of thedesired mask. Liquid masking composition is solidified producing amatrix 174 of solid mask 156 and porous medium 148. Matrix 174 is thenpatterned, e.g., by etching or ablating selected areas of the matrix toa depth at least equal to the depth of the matrix “layer”, to formelectroplating article 176. Alternately, the method can includesaturating the entire porous medium with liquid masking composition,pattern curing the liquid masking composition, and removing the uncuredmasking composition.

Other methods of forming electroplating articles include, e.g., applyingmasking composition selectively to a support by such processes as screenprinting, stencil printing and inkjet printing; and for porous mediums,melting a surface layer of the porous medium and forming negativefeatures in the surface of the porous medium by etching/ablating throughthe melted layer to expose the pores of the porous medium and generate arelief pattern. The methods for forming electroplating articles can alsoinclude etching the negative features (i.e., windows) of the maskpattern to increase the amount of relief on the electroplating article.In the case of a porous medium and a printed silicone mask, etching canbe conducted by an oxygen plasma.

The Electroplating Method

In general, select embodiments of the invention features electroplatingmethods that include contacting a substrate to be plated with anelectroplating article; selectively electroplating a first metal, e.g.,a support or sacrificial metal; and electroplating a second metal, e.g.,a structural metal. The step of electroplating a second metal caninclude selectively electroplating the second metal using anelectroplating article or blanket depositing the second metal. Theelectroplating method can be used to plate a single layer of metal orthe method can be repeated such that additional metal is plated ontopreviously plated metal layers producing a multi-layered structure.After a predetermined number of layer(s) have been plated, at least aportion of the support metal can be removed, e.g., by etching. Thestructural metal that remains defines a microscopic or mesoscopicdevice.

The method can also employ two electroplating articles to plate a singlelayer of one metal. Referring to FIGS. 10 a-10 c, a first metal isplated in a first pattern 230 (FIG. 10 a), the same metal is then platedin second pattern 232 (FIG. 10 b), to form plated metal layer 234 (FIG.10 c). Second pattern 232 may overlap first pattern 230.

One example of an electroplating method of an embodiment of theinvention is shown in FIGS. 11 a-11 m. The method includes contacting asubstrate to be plated 2 (FIG. 11 a) with first article 4 a, whichincludes mask 6 and support 8 (FIG. 11 b), in the presence of a firstmetal ion source (i.e., electrolyte and anode 10); depositing a firstmetal 12 (FIGS. 11 b and 11 c), e.g., a sacrificial metal; contactingsubstrate 2 with a second article 14 a, which includes mask 16 and asupport 18, depositing a second metal 20, e.g., a structural metal, inthe presence of a second metal ion source (i.e., electrolyte and anode22) (FIG. 11 d; optionally planarizing the layer; and repeating thismethod using differently patterned electroplating articles 4 b, 4 c, 14b, 14 c (FIGS. 11 e-11 k) to produce multi-layered structure 24 (FIG. 11l), which, after etching all of sacrificial metal 12, becomes element 26(FIG. 11 m). The second article can include a mask that has oversizedpositive features such that the surface area of one or more positivefeatures of the mask extends beyond the corresponding surface area ofthe first plated metal.

The element formed during the electroplating method can remain attachedto the substrate or can be removed from the substrate. One method forremoving the element includes plating a first layer of support materialonto the substrate such that etching removes the source of attachment ofthe element to the substrate.

Another electroplating method is depicted in FIGS. 12 a-12 c. Theelectroplating method includes: contacting a substrate to be plated 2with an electroplating article (not shown); selectively depositing afirst metal 12 (i.e., either the structural or the support metal) (FIG.12 a); blanket depositing a second metal 20 (FIG. 12 b), andmechanically planarizing the deposited layer to achieve a flat, smoothlayer 28 of precise thickness (FIG. 12 c). The planarized surface can berinsed to remove abrasive particles present on the surface. Preferablythe support metal is selectively plated and the structural metal isblanket deposited.

Examples of useful planarization methods include mechanical (e.g.,diamond lapping and silicon carbide lapping), chemical-mechanical, andnon-mechanical (e.g., electrical discharge machining), planarizationprocesses. Diamond lapping is a particularly preferred planarizationprocess. Diamond lapping can be performed using a single grade ofdiamond abrasive, e.g., about 1-6 micron, or diamond abrasives ofvarious grades. Lapping with different grades of abrasive can beperformed using separate lapping plates, or in different regions of asingle plate. For example, a coarse diamond abrasive can be applied tothe outer region of a spinning circular lapping plate, and a finediamond abrasive can be applied to the inner region. A removablecircular wall can be provided between the inner and outer regions toincrease segregation. The layer to be planarized first contacts theouter region of the plate, is then optionally rinsed to remove coarseabrasive, and then is moved to the inner region of the plate. Theplanarized surface can then be rinsed using a solution, e.g.,water-based or electrolyte-based solution, to remove both abrasive andabraded particles from the planarized layer. The abrasive slurrypreferably is easily removable, e.g., water-soluble. Layer thickness,planarity and smoothness can be monitored, e.g., using an opticalencoder, wear resistant stops, and by mating the layer under a knownpressure with a precision flat metal plate and measuring the resistanceacross the plate-layer junction. Thickness of the plated metal can alsobe measured by, for example, contacting the plated metal with a maskhaving a pattern that is complementary to the plated metal pattern andmeasuring the displacement.

One example of a preferred planarization process includes allowing thework piece, i.e., the substrate having the layer to be planarized, torotate within a “conditioning ring” on the lapping plate. Lapping canalso be performed by moving a workpiece around the surface of a lappingplate using the X/Y motion stages of the electroplating apparatuswithout rotating or releasing the workpiece. In this way, the tangentialmotion of the plate with respect to the substrate rotates through 360degrees. The timing of slurry delivery may be synchronized to the motionof the substrate such that the slurry is delivered to the plate.Movement of the workpiece can occur in paths other than circularincluding a path having a sinusoidal orbit of the form r=r0+A sin Bθ.

The substrate to be plated can include a conductive surface or anonconductive surface provided with a conductive layer. The substrate tobe plated can be planar or nonplanar. The substrate to be plated canalso be a previously electroplated or deposited metal or a layer thatincludes at least one metal.

The electroplating method can be performed, e.g., on an integratedcircuit. One example of an electroplating method performed on anintegrated circuit is shown in FIGS. 13 a-13 i. To permit electricalcontact during plating, the aluminum pads can be connected to conductorsthat terminate at distant contact pads, which can be temporarily tiedtogether by a bus. Referring to FIGS. 13 a-13 i, the electroplatingmethod of this embodiment includes: spin coating a layer of polyimide 34onto thin copper disk 36; adhering copper disk 36 to bottom surface ofsilicon wafer 38 with the polyimide coated surface of the copper diskcontacting the bottom surface of the wafer (FIG. 13 b), which includesaluminum pad 40, narrow conductor 42, contact pad 41, and passivationlayer 44 (FIGS. 13 a and 13 b); partially sawing through wafer 38 toassist separation of the die after processing; spin coatingphotosensitive polyimide 35 on the top surface of wafer 38 to protectaluminum pads 40 and 41 during subsequent etching and to fill saw line46; patterning polyimide to expose pads 40 to be plated and pads 41 forelectrical contact (FIG. 13 c); degreasing wafer; immersing thestructure in zincate plating solution; applying photoresist andpatterning to create a bus; joining contact pads 41 by sputtering ofcopper to form a bus 48 (FIG. 13 d) that is in contact with pads 41 forthe electroplating method; patterning resist 35 over bus 48 to preventnickel from depositing on bus 48; plating enough nickel 50 (FIG. 13 e)on aluminum pad 40 to allow planarization; removing the resist 35;making electrical contact with the plated metal; sputtering a planarbase 51 and plating a sufficient amount of copper 52 over the entirewafer surface to allow planarization; planarizing surface to exposenickel 50 (FIG. 13 g); electroplating the layers of the microstructure(FIG. 13 h); etching copper 51 and 52 including bus 48 and copper disk36; and stripping polyimide 34 thereby defining microstructure device 54attached to wafer 38 (i.e., the integrated circuit) (FIG. 13 i).

The electroplating methods can employ cyclic plating to improveuniformity of the deposited metal layer. Cyclic plating includes verybriefly interrupting the current applied to the electrode insynchronization with removing the mask from the substrate to be plated,which simultaneously replenishes the electrolyte additives, vents anygases, and discharges particulates and broken-down additives from themicrovolume defined by the support, the substrate to be plated, and themask. Current is then re-applied in synchronization with contacting,i.e., remating, the mask with the substrate. This method can be repeateduntil the desired thickness of metal has been deposited. The walls ofthe mask can be given a slight taper or draft (i.e., negative featuresdefined by the mask are slightly larger on the side of the maskcontacting the substrate), to facilitate repeated contact of a mask witha substrate in the presence of a deposit of incomplete thickness.

Uniformity of the plated metal layer can be improved by controllingcurrent density and adjusting current density on a feature-by-featurebasis by controlling the local thickness, and optionally the localporosity, of the support of the electroplating article. Uniform platingcan also be achieved by using an insoluble anode as a support, where theinsoluble anode has a thin layer of a soluble coating located thereonthat has a thickness calculated to provide the desired thickness ofplated metal on the substrate. Once the finite amount of ions in thevolume of electrolyte within the area defined by the mask (includingions created from any soluble coating that was initially part of theanode) are consumed plating ceases and the coating and the substrate areplated. As long as the initial coating on the insoluble anode is uniformin thickness, the plated metal will be uniform in thickness.

Hydrogen bubble formation can also be minimized by employing a lowcurrent density to increase current efficiency; decreasing temperatureand/or pressurizing the electrolyte in bulk to increase the solubilityof hydrogen in the electrolyte; employing a mask material that isimpermeable to the electrolyte but gas permeable (e.g., a hydrophobicmicroporous material); performing the electroplating method under vacuumso that gas bubbles are pulled out of the mask features; employingantipitting agents (e.g., SNAP for nickel sulfamate electrolytes) tominimize the formation of pits by reducing the attachment of the gasbubbles to the substrate; increasing the masking pressure, which canlocally increase electrolyte pressure due to reduced microvolume, whichwill establish large pressures on the electrolyte in localized areaskeeping hydrogen in solution; and incorporating hydrogen gettering agentinto the mask material (e.g., by mixing a fine powder into the liquidmasking composition).

Examples of useful etching compositions for selectively stripping copperfrom nickel structures include: solutions of ammonium hydroxide andcopper sulfate, solutions of ammonium hydroxide and sodium chlorite,with ammonium hydroxide-copper sulfate solution being preferred foretching structures attached to CMOS devices, and Enstripe C38commercially available from Enthone OMI. Etching can also be performedin the presence of vibrations, e.g., ultrasound applied to the etchantor the substrate that was plated, pressurized jets of etchant contactingthe metal to be etched, and surfactant. Flash present on the structuralmetal, e.g., in the form of thin projections extending from the surfaceof the structural metal, can be removed, e.g., by acid etching orelectropolishing.

The electroplating methods can be used to manufacture elements havingcomplex microstructure and close tolerances between parts. One exampleof a method for manufacturing elements having parts that fit with closetolerances, e.g., gaps between the parts are between about 1-5 um,involves electroplating the parts of the device in an unassembled,preferably pre-aligned, state. Once manufactured, the individual partscan be moved into operational relation with each other. Referring toFIGS. 14 a-14 e, a method of manufacturing device 188 including gear 190and shaft 192 having retaining clips 200 includes the electroplatingmethods disclosed above. Assembly fixture 194 is plated in a pre-alignedlocation with gear 190 (FIG. 14 a). Chuck 196 (e.g., electromagnetic orvacuum) secures the assembly fixture pieces 194 as support material 198is etched (FIG. 14 b). During etching gear 190 may fall into contactwith shaft 192. Chuck 196 is then lowered, causing assembly fixture 194to press gear 190 over retaining clips 200 on shaft 192 and into finalposition, as shown in FIG. 14 c. Chuck 196 is then raised removingassembly fixture 194 from the completed device 188, as shown in FIGS. 14d and 14 e.

The electroplating method can also be used to manufacture elements inwhich at least a portion of the support metal (i.e. normally sacrificialmetal) is enclosed within the structural material such that the enclosedsacrificial metal is not etched away during the removal process and thusbecomes part of the structure of the element. Referring to FIGS. 15 aand 15 b, a cross section of a plated element 236 (FIG. 15 b) is shownin which support metal 238 remains encapsulated within structural metal240 after the portion of support metal 238 that is accessible by etchant(FIG. 15 a) is removed.

The electroplating processes can also be used to manufacture tooling formolding (e.g., injection molding, metal injection molding, reactioninjection molding, thermoforming, blow molding, and die casting). Moldinserts can be manufactured by orienting mold inserts so that theejection axis of the part is parallel to the stacking axis of the layersand the parting surface of the part to be molded is the last layerdeposited. The electroplating methods can be used to form parts (i.e.elements) that include undercuts as shown in FIG. 16 a, to form partswithout draft as shown in FIG. 16 b, and to form molds without undercutsand with draft by depositing layers of structural material where eachsubsequently plated layer of structural metal lies entirely within theboundary of the previously deposited layer (e.g., layers 801-805) ofstructural metal, as shown in FIG. 16 c. The object produced by the moldof FIG. 16 c is shown in FIG. 16 d. The mold of 16 c can optionally beproduced without the use of a support (i.e. sacrificial) material.Referring to FIG. 16 c, layer 801 is deposited before layer 802, and soon.

Electroplating Apparatus

The electroplating method can be performed in a variety ofelectroplating apparatus. One particularly useful apparatus for carryingout an electroplating method is shown in the side view of FIG. 17.Apparatus 56 includes two baths 58, 60 (e.g., a nickel plating bath anda copper plating bath), and an inspection station 62. Each bath 58, 60is constructed to be capable of electroplating a different metal. Eachbath 58, 60 includes an electrolyte, an anode 59, 61, and anelectroplating article 4, 14. As shown, apparatus 56 accommodates asingle substrate to be plated 2. The apparatus can be constructed toaccommodate multiple substrates to be plated and multiple electroplatingarticles. Each article 4, 14 includes at least one patterned conformablemask 6,16 and is capable of depositing a pattern of metal.

The mechanical and electrochemical control of the electroplatingapparatus can be controlled by computers to implement the electroplatingmethod. Substrate to be plated 2 is transported by precision motionstages 64 x, 64 y, 64 z, equipped with DC servo motors, stepper motorsor combinations thereof, and precision encoders, between plating baths58, 60 and rinsing station 66. Substrate 2 suspended on chuck 68 entersfirst bath 58, positions itself over mask 6, contacts mask 6, andundergoes plating. After a predetermined thickness of metal has beenplated onto substrate 2, substrate 2 is removed from bath 58, rinsed andtransferred to second plating bath 60 where it contacts a second mask16, undergoes plating to a predetermined thickness (preferably the samethickness of the first deposited metal), is rinsed, and is returned tofirst bath 58. Inspection station 62, including a high-resolution videomicroscope system with PC frame grabber, can be used in conjunction withcontrol software to automatically record images of the deposited layersto a hard disk. Preferably apparatus 56 is enclosed in a sealed chamberand equipped with a vacuum system to degas the mask.

Useful mechanisms for applying controlled, uniform pressure to thesubstrate include applying a fluid pressure (e.g., through a pneumaticor hydraulic cylinder). One particularly preferred method for applyinguniform pressure across a circular substrate includes applying pressureat the center of the substrate through a ball joint (e.g., a ballsandwiched between the cylinder or extension thereof and the substrate,possibly retained by a countersink in each). The ball allows thesubstrate to tilt as needed to conform to the mask surface and to findan equilibrium position within which pressure is uniformly distributed.The substrate can be held against the ball by surrounding the substratewith a tight-fitting flexible tube that is anchored at one end to themoving member.

A very stiff, precision mechanical slide (e.g., a mechanical slide thatincorporates crossed roller bearings) can be used to provide repeatablepositioning of the mated substrate. The stages that move in the plane ofthe deposited layer, X/Y stages, can be fixed in location by clamps(e.g., an electromagnetic brake).

The device (e.g., the chuck) that carries the substrate to be plated caninclude a sliding insulating tube that moves into position as metallayers are added to the substrate. Referring to FIGS. 17 and 18, slidinginsulating tube 67 is shown in cross section in contact with edge mask244 on support 14 and surrounding substrate 2 and plated metal layers250.

The electroplating apparatus can be modified to include a device capableof directing a spray of electrolyte into the volume defined by thenegative features of the article just prior to contacting the article tothe substrate to be plated.

The electroplating apparatus can include a filtration system to controlparticulate contamination within the apparatus. After the electroplatingarticles and substrate(s) are loaded into the electroplating apparatus,the apparatus can execute a self-cleaning cycle that includespressurized rising, ultrasonic agitation, and filtration. The air withinthe apparatus can be cleaned by a filtration system, e.g., a HEPAfiltration system. The air and electrolyte filtration processes canoperate continuously throughout the electroplating method. Theelectrolyte filtration system can be incorporated into a heating andpumping system to continuously circulate and warm the electrolyte tomaintain homogeneous concentration and constant temperature.

The thickness of the plated metal and plated metal layer can becontrolled, e.g., by measuring the deposition rates of the metals andplating for a predetermined period; monitoring the integrated current,with adjustments for plating efficiency, normalizing for calculated maskarea and calculating plating thickness; and through closed loopthickness control. The closed loop system includes inputting anestimate, based upon measured metal plating rates, into the softwarethat controls the electroplating method; plating a first metal to lessthan the desired thickness, pressing the substrate against a secondelectroplating article, such that the mask of the electroplating articlecontacts the first plated metal; forcing the substrate to move away fromthe support by an amount equal to the thickness of the plated layer;reading the thickness of the first plated metal using a high resolution(e.g., 0.1 um) encoder, linked to the substrate chuck; inputting thisdata into the software to update the stored rate value for the firstmetal; plating the remaining thickness of the first metal layer. Thisprocess and its complement for measuring the plating thickness of thesecond plated metal can be repeated every few layers as a calibration.

The position and orientation of the mask of the electroplating articlewith respect to the substrate and motion axes of the electroplatingapparatus (described below) can be determined by an alignment procedurethat uses reserved areas on the substrate to be plated and at least twodistantly separated masks, each bearing an alignment pattern. To alignthe mask to the substrate, a thin layer of metal is plated onto thealignment pattern of the substrate, the rotational and translationalmisalignment of the mask with respect to the substrate is measured,e.g., using a video microscope, and corrections. Alignment accuracy canbe verified by stripping the plated patterns and re-plating newpatterns. Alignment can be repeated throughout the electroplating methodas necessary.

Another example of a useful alignment method employs a vernier patternin which a pattern of fine lines having a first pitch is deposited overa second pattern of lines having a different pitch. The pitch spacing ofthe deposited pattern compared to the existing pattern provides anindication of the alignment error.

Referring to FIG. 19, a portion of another electroplating apparatus 66that includes bath 68 containing ions of a first metal, e.g., a nickelplating bath, bath 70 containing ions of a second metal, e.g., a copperplating bath, and multiple electroplating articles 72 a-f and 74 a-e, isshown. Each substrate to be plated (2 a-2 e) enters the apparatus 66 atthe left end 76 of bath 68, contacts article 72 a, becomes plated with afirst metal in the pattern of the mask of article 72 a, transfers tobath 70 after rinse (not shown), contacts article 74 a, becomes platedwith a second metal in the pattern of the mask on article 74 a,transfers to article 72 b after rinse (not shown), in bath 68 and so on.As depicted, substrate 2 a has received deposits of the first metal andthe second metal for the first three layers of the microstructure andthe first metal portion of the fourth layer. Substrate 2 b is one layerbehind substrate 2 a; substrate 2 c is two layers behind substrate 2 a,etc.

For elements (e.g., devices) that require dozens or hundreds ofdeposited layers, the electroplating system can be arranged in anannular design in which the electroplating articles are arranged inrings and in which the individual electroplating articles are replacedafter having contacted each of the substrates to be plated. One exampleof an apparatus for mass-producing electroplated structures is shown inFIG. 20. Apparatus 78 is designed to process 24 eight-inch diametersubstrates 2. Apparatus 78 is concentric in design and includes an outerring 80, and a middle ring 82 and a central disk 85. Outer ring 80includes electrolyte bath 84 and electroplating articles (not shown) forselectively plating a first metal. Middle ring 82 includes anelectrolyte bath 86 for blanket-plating a second metal. As opposed toblanket plating, middle ring 82 can include electroplating articles forselectively plating the second metal. Rotating lapping plate 85 (ifrequired), for planarizing the plated metal layers, is located at thecenter of apparatus 78. All processes (first metal selective plating,second metal blanket or selective plating and, optionally,planarization) occur during a single cycle, but on different substrates2. At the end of the cycle, the substrates undergoing plating move inthe pattern shown, in part, by arrows. Eight layers have been depositedafter having completed all of the cycles in the system and arriving backat the starting point. Prior to the first substrate arriving back at thefirst plating article, the first plating article can be replaced by anew plating article. Likewise after the other plating articles havecontacted each of the substrates they can be replaced, and substrates 2can continue around apparatus 78, receiving as many layers as arerequired for the device being made. Rinsing stations are not shown butcan be located in the spaces between the plating articles. It isanticipated that such an apparatus would permit the simultaneousmanufacture of about 2.5 million devices, each 500 microns square by 200microns tall, in an 8-hour period.

The electroplating apparatus can also include a single bath containingions of at least two metals (e.g., a Watts bath with added coppersulphate). A method for selectively depositing two metals from a commonplating bath of their ions is described in H. Yahalom and O. Zadok,“Formation of Compositionally Modulated Alloys by Electrodeposition,” J.Material Sci., Vol. 22, p. 494 (1987). The plating bath includes atleast two electroplating articles, each of which is dedicated to platingone of the metals. The articles can include a single mask pattern ormultiple mask patterns in a side-by-side arrangement on the surface ofthe support. In the case of an article having multiple mask patterns,the substrate can contact the different mask patterns in a predeterminedsequence, alternating with the mask pattern(s) on the second article, tobuild a three dimensional structure. Referring to FIG. 21, anelectroplating apparatus 88 that includes a single bath 90 containingions of two metals, e.g., nickel and copper ions, articles for platingthe first metal 92, articles for plating the second metal 94, andsubstrates 2 a-e, is shown.

Each substrate 2 a-2 e enters apparatus 88 at the left end 96 of bath90, contacts electroplating article 92 a becomes plated with the firstmetal in the pattern of the mask of electroplating article 92 a,transfers to and contacts article 94 a, becomes plated with the secondmetal in the pattern of the mask on electroplating article 94 a,transfers to electroplating article 92 b, and so on. As depicted,substrate 2 a has received deposits of the first metal and the secondmetal for the first three layers of the microstructure and the firstmetal portion of the fourth layer. Substrate 2 b is one layer behindsubstrate 2 a, substrate 2 c is two layers behind substrate 2 a, and soon.

A variety of methods can be used to improve the copper deposition ratein a common bath electroplating system including, e.g., pulsing theplating current, increasing temperature (e.g., laser enhanced plating),pumping electrolyte through the support of the electroplating article,ultrasonic vibration, and increasing the copper content in the vicinityof the copper disk. One method for locally increasing the concentrationof copper includes galvanostatic dissolution of the copper anode whileplating onto a dummy substrate. By applying a current pulse at a densityof, e.g., about 20-50 mA/cm2, both nickel and copper are deposited ontothe dummy substrate until sufficient copper to form a layer (about 1-2um thick) is generated in the electrolyte located between the anode andthe substrate. At this point the dummy substrate is substituted with thereal substrate and the anode is replaced with a nickel anode. Copper isthen deposited potentiostatically.

Another method for locally increasing the concentration of copperincludes employing an electroplating article holder 98 as shown in FIG.22. The volume of electroplating article holder 98 contains copper richelectrolyte and is defined by side walls 100 of a cylinder, a poroussupport 102 having a conformable mask 104, and anode 106 (e.g., aninsoluble platinized titanium anode). Electroplating article holder 98includes inlet and outlet ports for transferring electrolyte (notshown). This electroplating article holder can be immersed within anickel-plating bath, optionally separated by a barrier through which thesubstrate can intermittently pass.

In general when there is a risk of spontaneous deposition onto asubstrate while not in contact with an electroplating article, thesubstrate preferably is biased at a more positive potential than that atwhich copper reduction would occur until the substrate has contacted thecopper-electroplating article and current has been applied. Similarly,when current is removed, the substrate preferably is again biased untilthe substrate is removed from the electrolyte or applied to anotherarticle and current is again applied.

Another electroplating apparatus is shown in FIG. 23. Apparatus 260includes baths 262, 264 (e.g., a nickel plating bath and a copperplating bath), by an inspection station 266, and lapping station 268.Each bath 262, 264 is constructed to be capable of electroplating adifferent metal. Each bath 262, 264 includes an electrolyte and an anode270, 272. Bath 264 also includes an electroplating article 274 forselectively depositing a first metal. Bath 262 is used for blanketdepositing a second metal. Bath 262 includes a mask 276 for insulatingthe sides of the structure (i.e. including the element) being fabricatedon substrate 2 to prevent metal from plating on the sides of either thesubstrate or the structure. Referring to FIG. 24, a portion ofelectroplating apparatus 260 in which substrate 2 is positioned withinelectroplating bath 262 and is insulated, in part, by mask 276 is shown.Substrate 2 includes a selectively deposited layer 278 and a blanketdeposited layer 280.

Referring to FIG. 25, an example of an electroplating apparatus thatincludes an electroplating article that includes a porous membrane isshown. Electroplating article 108, which is in contact with substrate tobe plated 2, includes a relatively more rigid porous medium 110 having arelatively more coarse porosity, and relatively thinner, flexible porousmembrane 112 having a relatively more fine porosity, and patterned mask114 adhered to membrane 112. Patterned mask 114 is in contact withsubstrate 2 and anode 116 is disposed beyond porous medium 110. A metaldeposit 118 is formed in the opening (i.e., within a negative feature)defined by mask 114.

Referring to FIG. 26, another example of an electroplating apparatus 120that employs a porous membrane 112 is shown. Porous membrane 112 ismounted as a drumhead on drum frame 122 in a way that allows for handingand processing, maintenance of position of the membrane 112 with respectto the substrate, and allows pressure to be exerted on porous membrane112 through rigid porous medium 110 contacting porous membrane 112.Porous membrane 112 is clamped between concentric O-rings 124, andpulled taut over a rigid porous medium, or, as shown, a cylindrical,hollow “barrel” 126 by tightening screws 128. If a barrel is used, rigidporous medium 110 is placed within barrel 126 so as to make contact withone side of membrane 112. Plating substrate 2 contacts the other side ofporous membrane 112. An intermediate compliant material (not shown)e.g., an open pore foam, may be disposed between porous membrane 112 andrigid porous medium 110 to provide a more uniform contact pressurebetween the mask and plating substrate 2.

Automated Processing

Various embodiments of the invention also feature a method forgenerating mask patterns of very thin cross section for a threedimensional structure and a method for automated electroplating thatincludes contacting electroplating articles having the generated maskpatterns in a predetermined sequence to form the three dimensionalstructure.

One such embodiment employs an automatic mask minimization algorithm foroptimizing the number of masks for a given geometry. Application of themethod to a valve like device 602, shown in FIG. 27, can be describedwith reference to perforated lines A-D which indicate cross sections ofthe device 602. Cross-sections B and C are identical and cross sectionsA and D are identical. A single mask can be used for cross sections Band C and another mask can be used for cross sections A and D. Thealgorithm compares the newly calculated cross sections for use with agiven metal with the previously calculated cross sections for the samedevice or possibly those used to make other devices. A new mask isgenerated if the difference between the two cross sections exceeds somepredetermined (e.g., user specified) tolerance. This allows the numberof masks to be minimized, allowing a greater number of layers to beproduced from fewer electroplating articles. The program also generatesan apparatus control file which directs the software that controls theelectroplating apparatus such that masks are selected in a predeterminedsequence corresponding to mask location within the electroplatingapparatus and the layer being plated. The system can also export alayout file representing the first cross section of the part to befabricated, allowing pad design for CMOS interfacing using a standardlayout editor. The system can also display calculated cross sections tothe user to allow error checking.

FIG. 28 is a functional block diagram of an exemplary computing systemfor calculation of cross sections of a three dimensional structure inaccordance with an embodiment of the present invention. As shown in FIG.28, system 610 may include a processor 612, a memory 614 (e.g., a randomaccess memory (RAM), and a program memory (for example, a writableread-only memory (ROM) such as a flash ROM)), input devices 616, andoutput devices 618. Processor 612 includes a central processing unit(CPU) that forms part of a general-purpose computer, such as a PC,Macintosh, or workstation. Memory 614 stores program code for executionby processor 612 including operating system code and application programcode, and generally represents a magnetic hard drive or other storagedevice in combination with a random access memory accessed by processor612. As one example, memory 614 could be realized in part by a storagedrive contacting removable storage media carrying the applicationprogram code. Input devices 616 include input media for entry of userinput, such as a keyboard, mouse, and the like. Output devices 618include display devices including a view screen that provides graphicoutput, e.g., a CRT or flat panel monitor, a printer (e.g., a desk topprinter, an inkjet printer, a laser printer, a photoplotter, and thelike), the electroplating apparatus, a linotronic printer and the like.

FIG. 29 is a flow diagram illustrating a method for generating maskgeometries and machine control parameters for fabrication of a threedimensional structure. When the user starts the application program, asindicated by reference numeral 620, processor 612 receives and processesinput corresponding to the three dimensional geometry of a structure tobe cross sectioned from input devices 616 as indicated by block 622.Processor 612 determines the extents in layer plane of the entiregeometry of the three-dimensional structure as indicated by block 623.Processor 612 sets M, the number of layers (including one or more crosssections), equal to 1 and generates cross sections for the Mth layer, asindicated by block 624. Processor 612 reads inputs relevant to each maskgeometry including, e.g., scaling of the three dimensional geometry,layer thickness, mask dimensions, number of copies and spacing, andtolerance for mask minimization, as indicated by block 625. Processor612 creates the geometry of mask corresponding to the Mth layer, asindicated by block 626, writes the geometry of the cross section(s) to amask pattern file, indicated by blocks 628 and 630, and writes maskidentification numbers for the Mth layer to a machine control file, asindicated by blocks 628 and 632. Memory 614 stores mask pattern in themask pattern file, as indicated at block 630. Memory 614 stores locationinformation in machine control file, as indicated at block 632.Processor 612 queries if additional layers are needed to complete thegeometry of the three-dimensional structure, as indicated at block 634.

If so, processor 612 increments N by 1 and compares the geometry of maskfor Mth layer with that of mask for M-Nth layer, as indicated at block642. If processor 612 calculates that the geometry of the Mth layer hasbeen compared to the geometry of each previous mask and no geometrymatches have occurred (i.e. a “no” answer to the inquiry of 654), thenprocessor 612 creates a geometry of the mask for the Mth layer, asindicated at block 656. Processor 612 then writes the geometry for theMth layer to the mask pattern file (as indicated by block 658), sends anoutput to the mask pattern file, as indicated by block 660, and writesmask identification number for the Mth layer to the machine control file(as indicated by blocks 650 and 652).

If not, processor 612 queries whether M-N is greater than or equal to 1as indicated at block 654.

If so, processor 612 increments N by 1 and compares the geometry of maskfor Mth layer with that of mask for M-Nth layer, as indicated at block642. If processor 612 calculates that the geometry of the Mth layer hasbeen compared to the geometry of each previous mask and no geometrymatches, then processor 612 creates a geometry of the mask for the Mthlayer, as indicated at block 656. Processor 612 then writes the geometryfor the Mth layer to the mask pattern file (as indicated by block 658),sends an output to mask pattern file, as indicated by block 660, andwrites mask identification number for the Mth layer to the machinecontrol file (as indicated by blocks 650 and 652).

Processor 612 queries whether additional layers are required to be madeof the three dimensional object (as indicated by block 634).

If so, processor 612 increments M by 1 and continues the process again.

If not, the process ends.

FIG. 30 is a flow diagram illustrating a method for electroplating ametal onto a substrate using patterned masks that represent a crosssectional slice of a three dimensional object. When the user starts theapplication program, as indicated by reference numeral 720, processor612 signals the electroplating apparatus to perform machineinitialization and sets M, the number of layers plated equal to zero, asindicated at block 722. Processor 612 increments M by 1 (as indicated byblock 724), sets P (i.e., the number of different metals to be plated)equal to 1 and optionally biases the substrate to prevent spontaneousdeposition of the metal (as indicated by block 726). Processor 612 readsmachine control file (indicated by block 730) to obtain controlinformation about the layer that is to be plated, and reads masklocation file (indicated by block 732) to obtain information about thelocation of the mask pattern to be plated. Processor 612 directs theelectroplating apparatus to align the substrate to be plated with themask for material P of layer M and to contact the substrate to the mask(indicated by block 728). Processor 612 optionally measures layerthickness, if necessary, as indicated by block 734. Processor 612receives input that the substrate is in contact with the mask and turnsoff substrate bias (if turned on), as indicated by block 736. Processor612 instructs apparatus to deposit material P for layer M, as indicatedby block 738. Processor 612 receives input that the cross-section hasbeen deposited and applies a bias to the structure, if required, asindicated by block 740. Processor 612 instructs apparatus to remove thesubstrate from contact with the mask (as indicated at block 742), and toplanarize layer M to predetermined thickness (if necessary), asindicated at block 744. Processor queries whether P is less than thenumber of metals of layer M, as indicated by block 746.

If so, processor 612 increments P by 1 (as indicated by block 748), anddrives the electroplating apparatus to align the substrate with a maskcorresponding to the new value for P (i.e., the P metal of layer M), asindicated by block 728. Processor 612 drives electroplating apparatus tocontact the substrate with the mask (as indicated by block 748), and theabove process is repeated until P is equal to the number of metals onlayer M.

Turning back to block 746, if P is not less than the number of materialson layer M, processor 612 queries whether M is the final layer (asindicated by block 750).

If so, processor 612 ends the electroplating process as indicated bynumeral 752.

If not, processor 612 increments M by 1 as indicated by block 724, andprocessor 612 drives the electroplating process until the final layerhas been plated.

The data processes and control processes of various embodiments of theinvention can be implemented in digital electronic circuitry, or incomputer hardware, firmware, software, or in combinations thereof. Thedata processes and control processes of various embodiments of theinvention can be implemented in a computer program product tangiblyembodied in a machine-readable storage device for execution by aprogrammable processor; and method steps of various embodiments of theinvention can be performed by a programmable processor executing aprogram of instructions to perform functions of those embodiments of theinvention by operating on input data and generating output. The dataprocesses and control processes of various embodiments of the inventioncan advantageously be implemented in one or more computer programs thatare executable on a programmable system including at least oneprogrammable processor coupled to receive data and instructions from,and to transmit data and instructions to, a data storage system, atleast one input device, and at least one output device. Each computerprogram can be implemented in a high-level procedural or object-orientedprogramming language, or in assembly or machine language if desired; andin any case, the language can be a compiled or interpreted language.Suitable processors include, by way of example, both general and specialpurpose microprocessors. Generally, a processor will receiveinstructions and data from a read-only memory and/or a random accessmemory. Storage devices suitable for tangibly embodying computer programinstructions and data include all forms of non-volatile memory,including by way of example semiconductor memory devices, such as EPROM,EEPROM, and flash memory devices; magnetic disks such as internal harddisks and removable disks; magneto-optical disks; and CD-ROM disks. Anyof the foregoing can be supplemented by, or incorporated in, ASICs(application-specific integrated circuits).

To provide for interaction with a user, the data processes and controlprocesses of various embodiments of the invention can be implemented ona computer system having a display device such as a monitor or LCDscreen for displaying information to the user and a keyboard and apointing device such as a mouse or a trackball by which the user canprovide input to the computer system. The computer system can beprogrammed to provide a graphical user interface through which computerprograms interact with users.

Other embodiments are possible. Although the above description isdirected to planar substrates, the substrate could be non-planar. Insuch embodiments, the electroplating article can be sufficientlyflexible to conform to the shape of the substrate surface, or shaped tomatch the surface. For example, the electroplating article could bewrapped around a cylindrical substrate. Masking pressure can be appliedto nonplanar substrates through a powdered medium that conforms to themask.

In addition, although the electroplating embodiments have been describedabove with respect to the use of two metals, a variety of materials,e.g., polymers, ceramics and semiconductor materials, and any number ofmetals can be deposited either by the electroplating methods describedabove, or in separate processes that occur throughout the electroplatingmethod. A thin plating base can be deposited, e.g., by sputtering, overa deposit that is insufficiently conductive (e.g., an insulating layer)so as to enable subsequent electroplating. Multiple support materials(i.e. sacrificial materials) can be included in the electroplatedelement allowing selective removal of the support materials.

The electroplating methods of various embodiments of the invention canbe used in combination with other processes. Referring to FIG. 31, forexample, electromagnetic motor 178 including armature windings 180connected to an integrated circuit at aluminum pads on substrate 182,can be formed by interrupting the electroplating method and etching aportion of the support metal (e.g., using a patterned resist) to producecavity 184 (i.e., the rotor core of the motor) defined by structuralmetal 186 serving as an etch stop. Cavity 184 is then filled with amagnetic powder (e.g., Ne—Fe—B), which is subsequently sintered andmagnetized. If necessary, metal is sputtered onto the sintered magneticpowder to establish a plating base and the electroplating method can beresumed. Such cavities can be filled with solids, fluids or evacuated toform a vacuum.

Where multiple metals are to be deposited, the metals can be selectivelydeposited on the substrate by masking only the substrate. By onlymasking the substrate, the metal being selectively plated onto thesubstrate is also deposited onto the previously deposited metals. Aftereach of the metals for a given layer has been deposited the layer isplanarized to the desired thickness. Alternatively, the mask can coverall of the previously deposited metals. In this alternative, the maskcan also be stepped in thickness to accommodate the topography of apartially plated substrate.

Another embodiment of the electroplating method involves manufacturing astructure well defined in shape and position according to the followingmethod: preparing a piece of rigid, high strength material with aninterconnected porosity (e.g., partly-sintered ceramic); shaping onesurface of this piece such that it has the inverse (in the mold makingsense) shape to that of the desired deposit; positioning the piece sothat its surface lies opposite the substrate to be plated, at thedesired position of the final deposit surface, and placing an anode onthe other side of it; plating metal onto the substrate while moving thepiece (continuously or periodically) with sufficient force and in such away that its surface still remains matched to that of the desireddeposit (for a planar surface, move it within the plane, for acylindrical surface, move it axially, etc.) (The movement can be avibration sufficiently large to shear and remove any portion of thedeposit that extends into the pores of the piece); continuing platinguntil the entire volume between the substrate and the piece is filledwith the deposit, at which point the deposit will have molded itself tothe shape of the piece. The piece can be disposed of, or periodicallyreconditioned by chemically flushing the piece with fluid, dissolvingthe clogging material or placing the clogged surface in contact with ananode and deplating it onto a substrate in an electrolyte.

Referring to FIGS. 32 a-32 d, another embodiment of an electroplatingarticle is shown. Electroplating article 200 includes a mask adhered toand coextensive with a patterned, rigid substrate (e.g.,polymethylmethacrylate). During the electroplating method a deposit isformed in the window(s) (i.e., negative mask features) of the article.More specifically, substrate 204 is contacted with a first patternedelectroplating article 200, as shown in FIG. 32 a; a first metal deposit206 is formed in a shape defined by the pattern 202 in firstelectroplating article 200, first article 200 is then removed (FIG. 32b); substrate 204 is then contacted in alignment with a second patternedelectroplating article 208 (FIG. 32 c), deposit 210 is formed, andsecond article 208 is removed (FIG. 32 d). The plated metal is thenplanarized and the method repeated until an element of sufficientthickness and dimension has been achieved. The electroplating articlescan include a region 210 of overlapping plated metal, which will have acorresponding greater thickness. The overlapping region can beplanarized to create a planar layer of deposited metal. Masking pressurecan be applied by pressing an anode or porous medium against theelectroplating article. The mask can be made stiffer by increasing itsthickness.

Although the electroplating methods have been described with respect tocontacting a cathode with an article and plating onto a cathode, it iscontemplated that the electroplating article can be placed in contactwith a substrate functioning as an anode such that metal is selectivelyremoved from the anode in a pattern corresponding to the pattern on theelectroplating article. Such a process can be employed to selectivelyetch, engrave, and polish a substrate, e.g., a plaque.

An electroplating method includes forming a layer, the forming of thelayer includes: a) contacting a substrate with a first article, thefirst article includes a support and a conformable mask disposed in apattern on the support; b) electroplating a first metal from a source ofmetal ions onto the substrate in a first pattern, the first patterncorresponding to the complement of the conformable mask pattern; and c)removing the first article from the substrate. The method may furtherinvolve one or more of (1) selectively depositing or non-selectivelydepositing one or more additional materials to complete formation of thelayer, (2) planarizing deposited material after each deposition or afterall depositions for a layer, and/or (3) forming layers adjacentpreviously formed layers to build up a structure from a plurality ofadhered layers. Electroplating articles and electroplating apparatus arealso disclosed.

What is claimed:
 1. A multi-layer structure, comprising: i. at least onefirst layer comprising at least one first planarized material; ii. atleast one second layer comprising at least one core material and atleast one second material, whereby the at least one second materialcompletely surrounds the sides of the at least one core material andwherein the at least one core material is completely bounded from belowby the first layer; and iii. at least one third layer comprising atleast one third planarized material wherein the third layer completelybounds the at least one core material of the at least one second layerfrom above; wherein the at least one core material is completelyencapsulated by a combination of the at least one first planarizedmaterial, the at least one second material, and the at least one thirdmaterial.
 2. The structure of claim 1 wherein the at least one firstmaterial is a single material.
 3. The structure of claim 2 wherein theat least one second material is a single material.
 4. The structure ofclaim 3 wherein the at least one third material is a single material. 5.The structure of claim 4 wherein the at least one first material, the atleast one second material, and the at least one third material is thesame material.
 6. The structure of claim 5 wherein the same materialcomprises nickel and the at least one core material comprises copper. 7.The structure of claim 5 wherein the at least one second layer is asingle layer.
 8. The structure of claim 1 wherein the at least one firstmaterial, the at least one second material, the at least one thirdmaterial, and the at least one core material are metals.
 9. Thestructure of claim 1 wherein at least one material of the at least onefirst material, the at least one second material, the at least one thirdmaterial, and the at least one core material comprises a materialselected from the group consisting of: (1) a polymer material, (2) aceramic material, (3) a semiconductor material.
 10. The structure ofclaim 1 wherein the structure is a microscopic structure.
 11. Thestructure of claim 1 wherein the structure is a mesoscopic structure.